diff --git a/app/code/Magento/GraphQl/etc/di.xml b/app/code/Magento/GraphQl/etc/di.xml
index fca6c425e2507..d6168cdc37600 100644
--- a/app/code/Magento/GraphQl/etc/di.xml
+++ b/app/code/Magento/GraphQl/etc/di.xml
@@ -29,6 +29,7 @@
         <arguments>
             <argument name="factoryMapByConfigElementType" xsi:type="array">
                 <item name="graphql_interface" xsi:type="object">Magento\Framework\GraphQl\Config\Element\InterfaceFactory</item>
+                <item name="graphql_union" xsi:type="object">Magento\Framework\GraphQl\Config\Element\UnionFactory</item>
                 <item name="graphql_type" xsi:type="object">Magento\Framework\GraphQl\Config\Element\TypeFactory</item>
                 <item name="graphql_input" xsi:type="object">Magento\Framework\GraphQl\Config\Element\InputFactory</item>
                 <item name="graphql_enum" xsi:type="object">Magento\Framework\GraphQl\Config\Element\EnumFactory</item>
@@ -64,6 +65,7 @@
                 <item name="Magento\Framework\GraphQl\Config\Element\Type" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputTypeObject</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\Input" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Input\InputObjectType</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\InterfaceType" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputInterfaceObject</item>
+                <item name="Magento\Framework\GraphQl\Config\Element\UnionType" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputUnionObject</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\Enum" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Enum\Enum</item>
             </argument>
         </arguments>
@@ -78,6 +80,7 @@
             <argument name="formatters" xsi:type="array">
                 <item name="fields" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Fields</item>
                 <item name="interfaces" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Interfaces</item>
+                <item name="unions" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Unions</item>
                 <item name="resolveType" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\ResolveType</item>
             </argument>
         </arguments>
@@ -85,6 +88,7 @@
     <type name="Magento\Framework\GraphQlSchemaStitching\GraphQlReader\TypeReaderComposite">
         <arguments>
             <argument name="typeReaders" xsi:type="array">
+                <item name="union_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\UnionType</item>
                 <item name="enum_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\EnumType</item>
                 <item name="object_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\ObjectType</item>
                 <item name="input_object_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\InputObjectType</item>
diff --git a/app/code/Magento/GraphQl/etc/schema.graphqls b/app/code/Magento/GraphQl/etc/schema.graphqls
index 2595ad09c072a..7366567c2b95d 100644
--- a/app/code/Magento/GraphQl/etc/schema.graphqls
+++ b/app/code/Magento/GraphQl/etc/schema.graphqls
@@ -30,14 +30,14 @@ directive @resolver(class: String="") on QUERY
     | OBJECT
     | FIELD_DEFINITION
     | ARGUMENT_DEFINITION
-    | INTERFACE
-    | UNION
     | ENUM
     | ENUM_VALUE
     | INPUT_OBJECT
     | INPUT_FIELD_DEFINITION
 
-directive @typeResolver(class: String="") on INTERFACE | OBJECT
+directive @typeResolver(class: String="") on UNION
+    | INTERFACE
+    | OBJECT
 
 directive @cache(cacheIdentity: String="" cacheable: Boolean=true) on QUERY
 
diff --git a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/Item.php b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/Item.php
index 1731a974aaed3..71ff93875f2c1 100644
--- a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/Item.php
+++ b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/Item.php
@@ -11,6 +11,9 @@
 use Magento\Framework\GraphQl\Config\Element\Field;
 use Magento\Framework\GraphQl\Query\ResolverInterface;
 
+/**
+ * Resolver for Item
+ */
 class Item implements ResolverInterface
 {
     /**
diff --git a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/TestUnion.php b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/TestUnion.php
new file mode 100644
index 0000000000000..592b0caaa88a3
--- /dev/null
+++ b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/TestUnion.php
@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\TestModuleGraphQlQuery\Model\Resolver;
+
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Query\ResolverInterface;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+
+/**
+ * Resolver for Union type TestUnion
+ */
+class TestUnion implements ResolverInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function resolve(
+        Field $field,
+        $context,
+        ResolveInfo $info,
+        array $value = null,
+        array $args = null
+    ) {
+        return [
+            'custom_name1' => 'custom_name1_value',
+            'custom_name2' => 'custom_name2_value',
+        ];
+    }
+}
diff --git a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/UnionTypeResolver.php b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/UnionTypeResolver.php
new file mode 100644
index 0000000000000..40cbdadb8a948
--- /dev/null
+++ b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/UnionTypeResolver.php
@@ -0,0 +1,27 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\TestModuleGraphQlQuery\Model\Resolver;
+
+use Magento\Framework\GraphQl\Query\Resolver\TypeResolverInterface;
+
+/**
+ * Type Resolver for union
+ */
+class UnionTypeResolver implements TypeResolverInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function resolveType(array $data): string
+    {
+        if (!empty($data)) {
+            return 'TypeCustom1';
+        }
+        return '';
+    }
+}
diff --git a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/etc/schema.graphqls b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/etc/schema.graphqls
index 7eb175a88e322..1a5796e07b08b 100644
--- a/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/etc/schema.graphqls
+++ b/dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/etc/schema.graphqls
@@ -3,6 +3,7 @@
 
 type Query {
     testItem(id: Int!) : Item @resolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\Item")
+    testUnion: TestUnion @resolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\TestUnion")
 }
 
 type Mutation {
@@ -18,3 +19,14 @@ type MutationItem {
     item_id: Int
     name: String
 }
+
+union TestUnion @doc(description: "some kind of union") @typeResolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\UnionTypeResolver")  =
+    TypeCustom1 | TypeCustom2
+
+type TypeCustom1 {
+    custom_name1: String
+}
+
+type TypeCustom2 {
+    custom_name2: String
+}
diff --git a/dev/tests/api-functional/testsuite/Magento/GraphQl/TestModule/GraphQlQueryTest.php b/dev/tests/api-functional/testsuite/Magento/GraphQl/TestModule/GraphQlQueryTest.php
index 2db06e383758f..0bbdf5a4c9803 100644
--- a/dev/tests/api-functional/testsuite/Magento/GraphQl/TestModule/GraphQlQueryTest.php
+++ b/dev/tests/api-functional/testsuite/Magento/GraphQl/TestModule/GraphQlQueryTest.php
@@ -10,7 +10,7 @@
 use Magento\TestFramework\TestCase\GraphQlAbstract;
 
 /**
- * Class GraphQlQueryTest
+ * Test for basic GraphQl features
  */
 class GraphQlQueryTest extends GraphQlAbstract
 {
@@ -100,4 +100,29 @@ public function testQueryViaGetRequestWithVariablesReturnsResults()
 
         $this->assertArrayHasKey('testItem', $response);
     }
+
+    public function testQueryTestUnionResults()
+    {
+        $query = <<<QUERY
+{
+    testUnion {
+      __typename
+      ... on TypeCustom1 {
+          custom_name1
+      }
+      ... on TypeCustom2 {
+          custom_name2
+      }
+    }
+}
+QUERY;
+
+        $response = $this->graphQlQuery($query);
+
+        $this->assertArrayHasKey('testUnion', $response);
+        $testUnion = $response['testUnion'];
+        $this->assertArrayHasKey('custom_name1', $testUnion);
+        $this->assertEquals('custom_name1_value', $testUnion['custom_name1']);
+        $this->assertArrayNotHasKey('custom_name2', $testUnion);
+    }
 }
diff --git a/lib/internal/Magento/Framework/GraphQl/Config/Element/Type.php b/lib/internal/Magento/Framework/GraphQl/Config/Element/Type.php
index 20d017cc71062..073fb2e795e87 100644
--- a/lib/internal/Magento/Framework/GraphQl/Config/Element/Type.php
+++ b/lib/internal/Magento/Framework/GraphQl/Config/Element/Type.php
@@ -73,7 +73,15 @@ public function getFields() : array
     /**
      * Get interfaces the type implements, if any. Return an empty array if none are configured.
      *
-     * @return string[]
+     * Example return array(
+     *     array(
+     *         'interface' => 'SomeDefinedTypeInterface',
+     *         'copyFields' => true
+     *     ),
+     *     ...
+     * ),
+     *
+     * @return array
      */
     public function getInterfaces() : array
     {
diff --git a/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionFactory.php b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionFactory.php
new file mode 100644
index 0000000000000..02d0a60064db6
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionFactory.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+use Magento\Framework\GraphQl\Config\ConfigElementFactoryInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
+use Magento\Framework\ObjectManagerInterface;
+
+/**
+ * Factory for config elements of 'union' type.
+ */
+class UnionFactory implements ConfigElementFactoryInterface
+{
+    /**
+     * @var ObjectManagerInterface
+     */
+    private $objectManager;
+
+    /**
+     * @param ObjectManagerInterface $objectManager
+     */
+    public function __construct(
+        ObjectManagerInterface $objectManager
+    ) {
+        $this->objectManager = $objectManager;
+    }
+
+    /**
+     * Instantiate an object representing 'union' GraphQL config element.
+     *
+     * @param array $data
+     * @return ConfigElementInterface
+     */
+    public function createFromConfigData(array $data): ConfigElementInterface
+    {
+        return $this->create($data, $data['types'] ?? []);
+    }
+
+    /**
+     * Create union object based off array of configured GraphQL.
+     *
+     * Union data must contain name, type resolver, and possible concrete types definitions
+     * The type resolver should point to an implementation of the TypeResolverInterface
+     * that decides what concrete GraphQL type to output. Description is the only optional field.
+     *
+     * @param array $unionData
+     * @param array $types
+     * @return UnionType
+     */
+    public function create(
+        array $unionData,
+        array $types
+    ) : UnionType {
+        return $this->objectManager->create(
+            UnionType::class,
+            [
+                'name' => $unionData['name'],
+                'typeResolver' => $unionData['typeResolver'],
+                'types' => $types,
+                'description' => isset($unionData['description']) ? $unionData['description'] : ''
+            ]
+        );
+    }
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionInterface.php b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionInterface.php
new file mode 100644
index 0000000000000..2d557e6dc5b84
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionInterface.php
@@ -0,0 +1,23 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
+
+/**
+ * Defines the contract for the union configuration data type.
+ */
+interface UnionInterface extends ConfigElementInterface
+{
+    /**
+     * Get a list of fields that make up the possible return or input values of a type.
+     *
+     * @return Type[]
+     */
+    public function getTypes(): array;
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionType.php b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionType.php
new file mode 100644
index 0000000000000..5b27d03360efc
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Config/Element/UnionType.php
@@ -0,0 +1,92 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+/**
+ * Class representing 'union' GraphQL config element.
+ */
+class UnionType implements UnionInterface
+{
+    /**
+     * @var string
+     */
+    private $name;
+
+    /**
+     * @var string[]
+     */
+    private $types;
+
+    /**
+     * @var string
+     */
+    private $typeResolver;
+
+    /**
+     * @var string
+     */
+    private $description;
+
+    /**
+     * @param string $name
+     * @param string $typeResolver
+     * @param string[] $types
+     * @param string $description
+     */
+    public function __construct(
+        string $name,
+        string $typeResolver,
+        array $types,
+        string $description
+    ) {
+        $this->name = $name;
+        $this->types = $types;
+        $this->typeResolver = $typeResolver;
+        $this->description = $description;
+    }
+
+    /**
+     * Get the type name.
+     *
+     * @return string
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Get a list of fields that make up the possible return or input values of a type.
+     *
+     * @return string[]
+     */
+    public function getTypes(): array
+    {
+        return $this->types;
+    }
+
+    /**
+     * Return the name of the resolver class that determines the concrete type to display in the result.
+     *
+     * @return string
+     */
+    public function getTypeResolver(): string
+    {
+        return $this->typeResolver;
+    }
+
+    /**
+     * Get a human-readable description of the type.
+     *
+     * @return string
+     */
+    public function getDescription(): string
+    {
+        return $this->description;
+    }
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Filter.php b/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Filter.php
index 0e5feeba3bade..5ec80b1d4692c 100644
--- a/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Filter.php
+++ b/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Filter.php
@@ -51,7 +51,7 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritDoc
      */
     public function applyArgument(
         SearchCriteriaInterface $searchCriteria,
diff --git a/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Sort.php b/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Sort.php
index 6ecb1896d685a..d312837e41686 100644
--- a/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Sort.php
+++ b/lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Sort.php
@@ -33,7 +33,7 @@ public function __construct(SortOrderBuilder $sortOrderBuilder = null)
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritDoc
      */
     public function applyArgument(
         SearchCriteriaInterface $searchCriteria,
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Fields.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Fields.php
index ad9fb675a6d70..3456f3c039a64 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Fields.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Fields.php
@@ -10,6 +10,7 @@
 use Magento\Framework\GraphQl\Config\Data\WrappedTypeProcessor;
 use Magento\Framework\GraphQl\Config\Element\Field;
 use Magento\Framework\GraphQl\Config\Element\TypeInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
 use Magento\Framework\GraphQl\Schema\Type\Input\InputMapper;
 use Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\FormatterInterface;
 use Magento\Framework\GraphQl\Schema\Type\Output\OutputMapper;
@@ -89,17 +90,20 @@ public function __construct(
     /**
      * @inheritdoc
      */
-    public function format(TypeInterface $configElement, OutputTypeInterface $outputType): array
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType): array
     {
-        $typeConfig = [
-            'fields' => function () use ($configElement, $outputType) {
-                $fieldsConfig = [];
-                foreach ($configElement->getFields() as $field) {
-                    $fieldsConfig[$field->getName()] = $this->getFieldConfig($configElement, $outputType, $field);
+        $typeConfig = [];
+        if ($configElement instanceof TypeInterface) {
+            $typeConfig = [
+                'fields' => function () use ($configElement, $outputType) {
+                    $fieldsConfig = [];
+                    foreach ($configElement->getFields() as $field) {
+                        $fieldsConfig[$field->getName()] = $this->getFieldConfig($configElement, $outputType, $field);
+                    }
+                    return $fieldsConfig;
                 }
-                return $fieldsConfig;
-            }
-        ];
+            ];
+        }
         return $typeConfig;
     }
 
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Interfaces.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Interfaces.php
index 659c3f604508d..761ba68e44521 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Interfaces.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Interfaces.php
@@ -8,7 +8,7 @@
 namespace Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter;
 
 use Magento\Framework\GraphQl\Config\Element\Type;
-use Magento\Framework\GraphQl\Config\Element\TypeInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
 use Magento\Framework\GraphQl\Schema\Type\OutputTypeInterface;
 use Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\FormatterInterface;
 use Magento\Framework\GraphQl\Schema\Type\Output\OutputMapper;
@@ -32,9 +32,9 @@ public function __construct(OutputMapper $outputMapper)
     }
 
     /**
-     * {@inheritDoc}
+     * @inheritDoc
      */
-    public function format(TypeInterface $configElement, OutputTypeInterface $outputType) : array
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType) : array
     {
         $config = [];
         if ($configElement instanceof Type && !empty($configElement->getInterfaces())) {
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/ResolveType.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/ResolveType.php
index 3a40e609eb952..553e8fe40efc2 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/ResolveType.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/ResolveType.php
@@ -8,7 +8,8 @@
 namespace Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter;
 
 use Magento\Framework\GraphQl\Config\Element\InterfaceType;
-use Magento\Framework\GraphQl\Config\Element\TypeInterface;
+use Magento\Framework\GraphQl\Config\Element\UnionType;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
 use Magento\Framework\GraphQl\Schema\Type\OutputTypeInterface;
 use Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\FormatterInterface;
 use Magento\Framework\ObjectManagerInterface;
@@ -32,12 +33,12 @@ public function __construct(ObjectManagerInterface $objectManager)
     }
 
     /**
-     * {@inheritDoc}
+     * @inheritDoc
      */
-    public function format(TypeInterface $configElement, OutputTypeInterface $outputType) : array
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType) : array
     {
         $config = [];
-        if ($configElement instanceof InterfaceType) {
+        if ($configElement instanceof InterfaceType || $configElement instanceof UnionType) {
             $typeResolver = $this->objectManager->create($configElement->getTypeResolver());
             $config['resolveType'] = function ($value) use ($typeResolver) {
                 return $typeResolver->resolveType($value);
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Unions.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Unions.php
new file mode 100644
index 0000000000000..75b6a58790a09
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/Formatter/Unions.php
@@ -0,0 +1,50 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter;
+
+use Magento\Framework\GraphQl\Config\Element\UnionType;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
+use Magento\Framework\GraphQl\Schema\Type\OutputTypeInterface;
+use Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\FormatterInterface;
+use Magento\Framework\GraphQl\Schema\Type\Output\OutputMapper;
+
+/**
+ * Add unions implemented by type if configured.
+ */
+class Unions implements FormatterInterface
+{
+    /**
+     * @var OutputMapper
+     */
+    private $outputMapper;
+
+    /**
+     * @param OutputMapper $outputMapper
+     */
+    public function __construct(OutputMapper $outputMapper)
+    {
+        $this->outputMapper = $outputMapper;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType): array
+    {
+        $config = [];
+        if ($configElement instanceof UnionType && !empty($configElement->getTypes())) {
+            $unionTypes = [];
+            foreach ($configElement->getTypes() as $unionName) {
+                $unionTypes[$unionName] = $this->outputMapper->getOutputType($unionName);
+            }
+            $config['types'] = $unionTypes;
+        }
+
+        return $config;
+    }
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterComposite.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterComposite.php
index 416b4122b7097..c36df11012017 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterComposite.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterComposite.php
@@ -7,11 +7,11 @@
 
 namespace Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper;
 
-use Magento\Framework\GraphQl\Config\Element\TypeInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
 use Magento\Framework\GraphQl\Schema\Type\OutputTypeInterface;
 
 /**
- * {@inheritdoc}
+ * @inheritDoc
  */
 class FormatterComposite implements FormatterInterface
 {
@@ -29,18 +29,19 @@ public function __construct(array $formatters)
     }
 
     /**
-     * {@inheritDoc}
+     * @inheritDoc
      */
-    public function format(TypeInterface $configElement, OutputTypeInterface $outputType) : array
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType): array
     {
-        $config = [
+        $defaultConfig = [
             'name' => $configElement->getName(),
             'description' => $configElement->getDescription()
         ];
+        $formattedConfig = [];
         foreach ($this->formatters as $formatter) {
-            $config = array_merge($config, $formatter->format($configElement, $outputType));
+            $formattedConfig[] = $formatter->format($configElement, $outputType);
         }
 
-        return $config;
+        return array_merge($defaultConfig, ...$formattedConfig);
     }
 }
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterInterface.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterInterface.php
index 7d40b743a6a06..a99237aa8843a 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterInterface.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/ElementMapper/FormatterInterface.php
@@ -7,7 +7,7 @@
 
 namespace Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper;
 
-use Magento\Framework\GraphQl\Config\Element\TypeInterface as TypeElementInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
 use Magento\Framework\GraphQl\Schema\Type\OutputTypeInterface;
 
 /**
@@ -18,9 +18,9 @@ interface FormatterInterface
     /**
      * Convert GraphQL config element to the object compatible with GraphQL schema generator.
      *
-     * @param TypeElementInterface $configElement
+     * @param ConfigElementInterface $configElement
      * @param OutputTypeInterface $outputType
      * @return array
      */
-    public function format(TypeElementInterface $configElement, OutputTypeInterface $outputType) : array;
+    public function format(ConfigElementInterface $configElement, OutputTypeInterface $outputType): array;
 }
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputMapper.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputMapper.php
index 046eeb5b1f93d..afe0d84de26f8 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputMapper.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputMapper.php
@@ -13,7 +13,7 @@
 use Magento\Framework\Phrase;
 
 /**
- * Map type names to their output type/interface/enum classes.
+ * Map type names to their output type/interface/union/enum classes.
  */
 class OutputMapper
 {
@@ -38,7 +38,7 @@ public function __construct(
      * @return OutputTypeInterface
      * @throws GraphQlInputException
      */
-    public function getOutputType($typeName)
+    public function getOutputType(string $typeName)
     {
         $outputType = $this->typeRegistry->get($typeName);
 
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputUnionObject.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputUnionObject.php
new file mode 100644
index 0000000000000..a63b7b7417527
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/Output/OutputUnionObject.php
@@ -0,0 +1,28 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Schema\Type\Output;
+
+use Magento\Framework\GraphQl\Config\Element\UnionType as UnionElement;
+use Magento\Framework\GraphQl\Schema\Type\UnionType;
+
+/**
+ * The 'union' type compatible with GraphQL schema generator.
+ */
+class OutputUnionObject extends UnionType
+{
+    /**
+     * @param ElementMapper $elementMapper
+     * @param UnionElement $configElement
+     */
+    public function __construct(
+        ElementMapper $elementMapper,
+        UnionElement $configElement
+    ) {
+        parent::__construct($elementMapper->buildSchemaArray($configElement, $this));
+    }
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/Type/UnionType.php b/lib/internal/Magento/Framework/GraphQl/Schema/Type/UnionType.php
new file mode 100644
index 0000000000000..a843c6c669acf
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/Type/UnionType.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Schema\Type;
+
+/**
+ * Wrapper for GraphQl UnionType
+ */
+class UnionType extends \GraphQL\Type\Definition\UnionType implements OutputTypeInterface
+{
+
+}
diff --git a/lib/internal/Magento/Framework/GraphQl/Schema/TypeFactory.php b/lib/internal/Magento/Framework/GraphQl/Schema/TypeFactory.php
index 3b31653382e3a..84f8d809c958e 100644
--- a/lib/internal/Magento/Framework/GraphQl/Schema/TypeFactory.php
+++ b/lib/internal/Magento/Framework/GraphQl/Schema/TypeFactory.php
@@ -13,7 +13,7 @@
 use Magento\Framework\GraphQl\Schema\Type\EnumType;
 use Magento\Framework\GraphQl\Schema\Type\ListOfType;
 use Magento\Framework\GraphQl\Schema\Type\NonNull;
-use Magento\Framework\GraphQl\Schema\TypeInterface;
+use Magento\Framework\GraphQl\Schema\Type\UnionType;
 
 /**
  * Factory for @see TypeInterface implementations
@@ -42,6 +42,17 @@ public function createInterface(array $config) : InterfaceType
         return new InterfaceType($config);
     }
 
+    /**
+     * Create an union type
+     *
+     * @param array $config
+     * @return UnionType
+     */
+    public function createUnion(array $config) : UnionType
+    {
+        return new UnionType($config);
+    }
+
     /**
      * Create an input object type
      *
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader.php
index 1e8b33f79854b..9845646e09fd5 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader.php
@@ -11,6 +11,7 @@
 use Magento\Framework\Config\FileResolverInterface;
 use Magento\Framework\Config\ReaderInterface;
 use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\TypeMetaReaderInterface as TypeReaderComposite;
+use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\InterfaceType;
 
 /**
  * Reads *.graphqls files from modules and combines the results as array to be used with a library to configure objects
@@ -21,6 +22,7 @@ class GraphQlReader implements ReaderInterface
 
     public const GRAPHQL_SCHEMA_FILE = 'schema.graphqls';
 
+    /** @deprecated */
     public const GRAPHQL_INTERFACE = 'graphql_interface';
 
     /**
@@ -69,7 +71,7 @@ public function __construct(
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      *
      * @param string|null $scope
      * @return array
@@ -178,7 +180,7 @@ private function parseTypes(string $graphQlSchemaContent) : array
     private function copyInterfaceFieldsToConcreteTypes(array $source): array
     {
         foreach ($source as $interface) {
-            if ($interface['type'] == 'graphql_interface') {
+            if ($interface['type'] ?? '' == InterfaceType::GRAPHQL_INTERFACE) {
                 foreach ($source as $typeName => $type) {
                     if (isset($type['implements'])
                         && isset($type['implements'][$interface['name']])
@@ -253,7 +255,7 @@ private function convertInterfacesToAnnotations(string $graphQlSchemaContent): s
     private function addPlaceHolderInSchema(string $graphQlSchemaContent) :string
     {
         $placeholderField = self::GRAPHQL_PLACEHOLDER_FIELD_NAME;
-        $typesKindsPattern = '(type|interface|input)';
+        $typesKindsPattern = '(type|interface|input|union)';
         $enumKindsPattern = '(enum)';
         $typeNamePattern = '([_A-Za-z][_0-9A-Za-z]+)';
         $typeDefinitionPattern = '([^\{]*)(\{[\s\t\n\r^\}]*\})';
@@ -328,13 +330,14 @@ private static function getModuleNameForRelevantFile(string $file): string
      */
     private function addModuleNameToTypes(array $source, string $filePath): array
     {
-        foreach ($source as $typeName => $type) {
-            if (!isset($type['module']) && (
-                ($type['type'] === self::GRAPHQL_INTERFACE && isset($type['typeResolver']))
-                    || isset($type['implements'])
-            )
-            ) {
-                $source[$typeName]['module'] = self::getModuleNameForRelevantFile($filePath);
+        foreach ($source as $typeName => $typeDefinition) {
+            if (!isset($typeDefinition['module'])) {
+                $hasTypeResolver = (bool)($typeDefinition['typeResolver'] ?? false);
+                $hasImplements = (bool)($typeDefinition['implements'] ?? false);
+                $typeDefinition = (bool)($typeDefinition['type'] ?? false);
+                if ((($typeDefinition === InterfaceType::GRAPHQL_INTERFACE && $hasTypeResolver) || $hasImplements)) {
+                    $source[$typeName]['module'] = self::getModuleNameForRelevantFile($filePath);
+                }
             }
         }
 
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/EnumType.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/EnumType.php
index e4dec7afdab0a..c6e0481c7490e 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/EnumType.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/EnumType.php
@@ -15,6 +15,8 @@
  */
 class EnumType implements TypeMetaReaderInterface
 {
+    public const GRAPHQL_ENUM = 'graphql_enum';
+
     /**
      * @var DocReader
      */
@@ -30,14 +32,14 @@ public function __construct(
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
     public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
     {
         if ($typeMeta instanceof \GraphQL\Type\Definition\EnumType) {
             $result = [
                 'name' => $typeMeta->name,
-                'type' => 'graphql_enum',
+                'type' => self::GRAPHQL_ENUM,
                 'items' => [] // Populated later
             ];
             foreach ($typeMeta->getValues() as $enumValueMeta) {
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InputObjectType.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InputObjectType.php
index 38159fac03b3b..2108a04d8a9ed 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InputObjectType.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InputObjectType.php
@@ -17,6 +17,8 @@
  */
 class InputObjectType implements TypeMetaReaderInterface
 {
+    public const GRAPHQL_INPUT = 'graphql_input';
+
     /**
      * @var TypeMetaWrapperReader
      */
@@ -49,7 +51,7 @@ public function __construct(
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
     public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
     {
@@ -57,7 +59,7 @@ public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
             $typeName = $typeMeta->name;
             $result = [
                 'name' => $typeName,
-                'type' => 'graphql_input',
+                'type' => self::GRAPHQL_INPUT,
                 'fields' => [] // Populated later
             ];
             $fields = $typeMeta->getFields();
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InterfaceType.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InterfaceType.php
index baadb4be61cf2..76550469d409e 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InterfaceType.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/InterfaceType.php
@@ -17,6 +17,8 @@
  */
 class InterfaceType implements TypeMetaReaderInterface
 {
+    public const GRAPHQL_INTERFACE = 'graphql_interface';
+
     /**
      * @var FieldMetaReader
      */
@@ -49,7 +51,7 @@ public function __construct(
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
     public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
     {
@@ -57,7 +59,7 @@ public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
             $typeName = $typeMeta->name;
             $result = [
                 'name' => $typeName,
-                'type' => 'graphql_interface',
+                'type' => self::GRAPHQL_INTERFACE,
                 'fields' => []
             ];
 
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/ObjectType.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/ObjectType.php
index ba8e46dd60557..3ad6d69eb5c9c 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/ObjectType.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/ObjectType.php
@@ -19,6 +19,8 @@
  */
 class ObjectType implements TypeMetaReaderInterface
 {
+    public const GRAPHQL_TYPE = 'graphql_type';
+
     /**
      * @var FieldMetaReader
      */
@@ -69,7 +71,7 @@ public function __construct(
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
     public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
     {
@@ -77,7 +79,7 @@ public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
             $typeName = $typeMeta->name;
             $result = [
                 'name' => $typeName,
-                'type' => 'graphql_type',
+                'type' => self::GRAPHQL_TYPE,
                 'fields' => [], // Populated later
             ];
 
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/UnionType.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/UnionType.php
new file mode 100644
index 0000000000000..5776901765b5a
--- /dev/null
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/Reader/UnionType.php
@@ -0,0 +1,106 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader;
+
+use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\TypeMetaReaderInterface;
+use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\MetaReader\FieldMetaReader;
+use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\MetaReader\DocReader;
+use Magento\Framework\GraphQlSchemaStitching\GraphQlReader\MetaReader\CacheAnnotationReader;
+
+/**
+ * Composite configuration reader to handle the union object type meta
+ */
+class UnionType implements TypeMetaReaderInterface
+{
+    public const GRAPHQL_UNION = 'graphql_union';
+
+    /**
+     * @var FieldMetaReader
+     */
+    private $fieldMetaReader;
+
+    /**
+     * @var DocReader
+     */
+    private $docReader;
+
+    /**
+     * @var CacheAnnotationReader
+     */
+    private $cacheAnnotationReader;
+
+    /**
+     * @param FieldMetaReader $fieldMetaReader
+     * @param DocReader $docReader
+     * @param CacheAnnotationReader|null $cacheAnnotationReader
+     */
+    public function __construct(
+        FieldMetaReader $fieldMetaReader,
+        DocReader $docReader,
+        CacheAnnotationReader $cacheAnnotationReader = null
+    ) {
+        $this->fieldMetaReader = $fieldMetaReader;
+        $this->docReader = $docReader;
+        $this->cacheAnnotationReader = $cacheAnnotationReader ?? \Magento\Framework\App\ObjectManager::getInstance()
+                ->get(CacheAnnotationReader::class);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function read(\GraphQL\Type\Definition\Type $typeMeta): array
+    {
+        if ($typeMeta instanceof \GraphQL\Type\Definition\UnionType) {
+            $typeName = $typeMeta->name;
+            $result = [
+                'name' => $typeName,
+                'type' => self::GRAPHQL_UNION,
+                'types' => [],
+            ];
+
+            $unionTypeResolver = $this->getUnionTypeResolver($typeMeta);
+            if (!empty($unionTypeResolver)) {
+                $result['typeResolver'] = $unionTypeResolver;
+            }
+
+            foreach ($typeMeta->getTypes() as $type) {
+                $result['types'][] = $type->name;
+            }
+
+            if ($this->docReader->read($typeMeta->astNode->directives)) {
+                $result['description'] = $this->docReader->read($typeMeta->astNode->directives);
+            }
+
+            return $result;
+        } else {
+            return [];
+        }
+    }
+
+    /**
+     * Retrieve the union type resolver if it exists from the meta data
+     *
+     * @param \GraphQL\Type\Definition\UnionType $unionTypeMeta
+     * @return string
+     */
+    private function getUnionTypeResolver(\GraphQL\Type\Definition\UnionType $unionTypeMeta): string
+    {
+        /** @var \GraphQL\Language\AST\NodeList $directives */
+        $directives = $unionTypeMeta->astNode->directives;
+        foreach ($directives as $directive) {
+            if ($directive->name->value == 'typeResolver') {
+                foreach ($directive->arguments as $directiveArgument) {
+                    if ($directiveArgument->name->value == 'class') {
+                        return $directiveArgument->value->value;
+                    }
+                }
+            }
+        }
+        return '';
+    }
+}
diff --git a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/TypeReaderComposite.php b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/TypeReaderComposite.php
index e9b899bb2bb5b..614c1e3a743a0 100644
--- a/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/TypeReaderComposite.php
+++ b/lib/internal/Magento/Framework/GraphQlSchemaStitching/GraphQlReader/TypeReaderComposite.php
@@ -25,7 +25,7 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritDoc
      */
     public function read(\GraphQL\Type\Definition\Type $typeMeta) : array
     {